1. Field of the Invention
This invention is directed to the field of illuminated emergency exit signs and emergency exit lights and more particularly to such signs and lights that are illuminated by light emitting diodes (LEDs) operating at very low and efficient power levels such that their use results in substantial energy savings over the operational lives thereof. In the preferred embodiments, the emergency exit signs include LED emergency lamps that may be fixed or adjustably mounted to the housings of the exit signs so as to provide illumination to light exit passageways in the event of an AC power outage. The invention is further directed to a unique capacitance circuitry for powering the message illuminating LEDs of exit signs in series with one another and with a charging circuit for backup batteries contained within the housings of the signs when the exit signs are power by an AC power source and wherein, when the AC power is interrupted, the message illuminating LEDs, and any emergency illuminating LEDs used in combination therewith, are powered in parallel circuits by the backup batteries.
2. Description of the Related Art
The use of emergency exit signs to mark routes to exit buildings is generally mandated by government agencies for safety reasons. Conventional emergency exit signs are hard wired to the AC power source within a building so as to be continuously illuminated. In the event of a power outage, batteries are provided within the signs which supply power to the lights mounted therein that illuminate one or more message panels defined by walls of the sign housing. Such panels may have translucent areas that provide an emergency message, such as “EXIT”.
Government agencies have also mandated that, in addition to the marking of exit passages, emergency lighting be automatically activated to illuminate emergency passageways in the event of a power failure that disrupts power to the interior lighting within a building. Conventionally, emergency lighting is provided by independent light sources, such as one or two flood or spot type incandescent bulbs that are associated with a wall mounted housing in which batteries are contained for powering the lights whenever the AC power within a building is interrupted. The emergency lighting units also include sensing and control circuits for activating the emergency lights whenever the AC power is terminated and charging circuits for supplying power to charge the batteries whenever the AC power is active.
To become more efficient and to reduce costs associated with the need to provide both emergency signs and emergency exit lighting, combination emergency exit signs and emergency exit lights have been developed wherein the emergency lights are mounted to the exterior of an exit sign. Such combination signs and lights are described in U.S. Pat. Nos. 5,797,673, 6,142,648 and 6,8487,798 to Logan et al. The combination signs and emergency lights require only one housing to be mounted to a wall or ceiling and only a single connection to be made to the electrical power circuit within a building, thereby reducing installation time and costs. However, exit signs and emergency light combinations using incandescent lights are rather large and bulky and are not energy efficient.
With the advent of lower power light sources, such as light emitting diodes (LEDs), and better battery construction, such as light weight and longer lasting nickel cadmium (NiCd) batteries, more efficient combination emergency exit and emergency lights have been developed. Because LEDs are much smaller than conventional incandescent or fluorescent lights, the LED combination signs and emergency lighting units can be more compactly contained in more esthetically pleasing housings which are also lighter in weight. Also, as the LEDs operate at much lower power levels, such as from 1 to 8 watts, when compared to more conventionally illuminated signs, the cost for powering the signs is significantly reduced. Another benefit obtained by using LED illumination in emergency signs is that the operating life of an LED is significantly greater than for conventional incandescent or fluorescent lights. Because emergency signs and emergency illumination are needed in so many places, the energy savings that can be achieved through the use of LED technology, should mandate the use of LEDs in all new installations.
In some combination signs, as is taught in U.S. Pat. No. 5,446,440 to Gleason et al, LEDs are mounted within a primary housing of the sign. A first number of the LEDs is used to illuminate the emergency message while separate LEDs are aligned with openings provided in the lower wall of the housing through which the light from the separate LEDs may be directed or reflected to provide emergency lighting. In other LED combination signs, the LEDs may be mounted to an outer portion of the sign housing such as disclosed in U.S. Pat. No. 7,114,840 to Hamrick.
Even in view of the significant improvement LEDs have brought to the field of emergency signs and lighting, there remains a need to further enhance the efficiency of such signs and lighting so as to make installation easier, to provide for reductions in manufacturing costs, to enhance the styling and compactness of such signs and lighting and to further provide greater efficiency in energy savings.